1. Field of the Invention
This invention relates to an apparatus for recording and reproducing information. This invention also relates to a method of recording and reproducing information.
2. Description of the Related Art
A known digital recording and reproducing apparatus compressively encodes an input video signal into a first digital video signal of a given code. Every segment of the first digital video signal which corresponds to a predetermined number M of frames (a plurality of frames) is processed as follows. Words of a given error correction code are generated in response to every M-frame-corresponding segment of the first digital video signal. The error correction code words and the M-frame-corresponding segment of the first digital video signal are combined into an M-frame-corresponding segment of a second digital video signal. The second digital video signal is subjected to modulation for record. The modulation-resultant video signal is recorded on a magnetic tape.
The known digital recording and reproducing apparatus reproduces a video signal from a magnetic tape. The reproduced video signal is subjected to demodulation. Every M-frame-corresponding segment of the demodulation-resultant digital video signal is separated into error correction code words and an M-frame-corresponding segment of a third digital video signal. The M-frame-corresponding segment of the third digital video signal is corrected into an M-frame-corresponding segment of a fourth digital video signal in response to the error correction code words. The fourth digital video signal is decoded into an original video signal. The known digital recording and reproducing apparatus outputs the decoding-resultant video signal, that is, the reproduced original video signal.
A first video signal which has been recorded on a magnetic tape can be edited by the known digital recording and reproducing apparatus. For example, a second video signal is recorded over a portion of the first video signal which follows an editing point. In this case, only the portion of the first video signal which precedes the editing point remains on the magnetic tape. In the known digital recording and reproducing apparatus, the first video signal results from the processing of video information M frames by M frames. Accordingly, it is desirable that the editing point coincides with the boundary between M-frame-corresponding segments of the first video signal. In this case, during playback implemented after the editing process, all the video information represented by the remaining portion of the first video signal on the magnetic tape can be reproduced. On the other hand, in the case where the editing point is in an intermediate part of an M-frame-corresponding segment of the first video signal, after the editing process, the video information represented by a remaining part of the M-frame-corresponding segment of the first video signal will fail to be reproduced during playback. Thus, in the known digital recording and reproducing apparatus, the minimum unit of movement of the editing point corresponds to M frames.
It is a first object of this invention to provide an apparatus for recording and reproducing information which can implement an editing process having a smaller unit of movement of an editing point.
It is a second object of this invention to provide a method of recording and reproducing information which can implement an editing process having a smaller unit of movement of an editing point.
A first aspect of this invention provides an information recording and reproducing apparatus comprising a memory for storing a signal whose amount corresponds to a minimum recording unit; first means for reproducing first data from a minimum recording-unit corresponding portion of a recording medium, the minimum-recording-unit corresponding portion containing a designated editing point; second means for storing the first data reproduced by the first means into the memory; third means for detecting a boundary between frames represented by the first data in the memory which has been stored thereinto by the second means, the detected boundary corresponding to the editing point; fourth means for storing an address of a storage segment in the memory which corresponds to the boundary detected by the third means; fifth means for replacing a first portion of the first data in the memory which corresponds to the address stored by the fourth means and later addresses by second data while leaving a second portion of the first data in the memory which corresponds to addresses preceding the address stored by the fourth means to generate third data composed of the second data and the second portion of the first data in the memory; and sixth means for recording the third data on the minimum-recording-unit corresponding portion of the recording medium.
A second aspect of this invention is based on the first aspect thereof, and provides an information recording and reproducing apparatus wherein information recorded on the recording medium is divided into pieces each corresponding to the minimum recording unit, and each of the pieces of the information has a fixed amount of data.
A third aspect of this invention provides a method of recording and reproducing information which uses a memory for storing a signal whose amount corresponds to a minimum recording unit. The method comprises the steps of reproducing first data from a minimum-recording-unit corresponding portion of a recording medium, the minimum-recording-unit corresponding portion containing a designated editing point; storing the reproduced first data into the memory; detecting a boundary between frames represented by the first data in the memory, the detected boundary corresponding to the editing point; storing an address of a storage segment in the memory which corresponds to the detected boundary; replacing a first portion of the first data in the memory which corresponds to the stored address and later addresses by second data while leaving a second portion of the first data in the memory which corresponds to addresses preceding the stored address to generate third data composed of the second data and the second portion of the first data in the memory; and recording the third data on the minimum-recording-unit corresponding portion of the recording medium.
A fourth aspect of this invention is based on the third aspect thereof, and provides a method wherein information recorded on the recording medium is divided into pieces each corresponding to the minimum recording unit, and each of the pieces of the information has a fixed amount of data.